This invention relates to a lightable nosing bar assembly comprising a profiled metal rail, which is adapted to be secured to a nose edge of a step of a stairway and is provided in a portion of its cross-section that is disposed below the level of the tread with a longitudinally extending recess, which at least in a section of its length is exposed toward the free environment in a direction having a horizontal component, also comprising transparent covering means for covering the exposed portions of the longitudinally extending recess, and an illuminating device, which is disposed in the recess behind the covering means and extends throughout the length of the nose edge.